This invention relates to a device for articulated connection between a control element and a control bar with a ball head according to the characterising definition of claim 1. In particular, the invention relates to a device designed to provide an articulated connection between a control element in the form of a pedal and a piston rod attached to a piston of a hydraulic cylinder.
Such devices are used for example in motorized vehicles where it is necessary to connect a pedal hinged to a pedal box to a piston rod with a ball head at its end to ensure its efficient operation, the other end of the piston rod being hinged at the piston or a clutch control or main brake cylinder. At the same time, compressive or pulling forces must be transmitted during a working cycle between the parts such as the pedal and the piston rod moving in their angular position in relation to each other depending on whether the pedal is being pressed down or released.
European patent specification EP 0 229 350 B1 discloses a generic articulated connection having a one-piece insert part which connects a pedal with a ball head of a piston rod ensuring efficient operation. The insert part made of plastic is clipped here into a part of the pedal which is approximately U-shaped and has a bearing socket to hold the ball head. The bearing socket has an undercut into which the ball head can be pressed as if it were a snap-in connection and serving the purpose of retaining the ball head in the bearing socket during operation. The insert part has a hopper-like inlet area at the entry to the bearing socket. During assembly of the known articulated connection, the ball head is pressed through the entry section into the bearing socket by forcing the undercut. The piston rod extends through the entry area when this articulated connection is in its assembled condition or in operation.
A disadvantage of this state of the art can be seen in the fact that there is a danger, particularly at high temperatures, of the ball head permanently deforming the undercut at the bearing socket when a higher tension load is applied to the piston rod, possibly resulting in unacceptable play at the controls or, in the worst instance, in the ball head even being forced out of the bearing socket when the pedal is moved back rapidly and uncontrollably from its control position to its resting position or when it is pulled by the pedal.
The purpose of the invention is to create a device of the simplest possible design, to provide an articulated connection between a control element and a control rod with a ball head guaranteeing a reliable connection between the control element and a control rod which would be permanently backlash-free or have little backlash.
According to the present invention, there is provided a device to provide an articulated connection between a control element and a control rod with a ball head, the device having a main body, attachable at the control element, that envelops a locator section, for positive location of the ball head and that has an opening section, through which the control rod extends when the device is assembled; wherein the locator section is in two parts, the main body forming one of said parts and having a joint duct located outside the opening area, into which the ball head can be introduced, the other part of the locator section being formed by a molding insertable in the joint duct.
In particular the locator section enclosed by the main body locatable at the control element on a device of a generic type is in two parts, the main body forming one part into which the ball head can be introduced through a joint duct located outside the opening area surrounding the piston rod in operation, while a molding insertable in the joint duct forms the other part of the locating section.
In this design of articulated connection, the ball head is enveloped to a greater degree than according to the known state of the art; in other words, it can be said that the size of the undercut at the locator section provided for positive location of the ball head in the direction of the opening area, that is in the direction in which the main part of the control forces are acting in operation, can be made larger. This is not hindered by the assembly of the articulated connection because the undercut at the locator section in the direction of the opening area does not have to be overcome when joining the ball head since it is on the other hand possible to join the ball head to the main body through the joint duct which is outside the opening area before the locator section is completed by inserting the molding. Therefore, the direction in which the ball head is joined to the main body is different from the direction in which most of the operating forces act, that is different than in the case of the state of the art referred to.
As a result, the mechanical capacity of the articulated connection is improved and greater forces can be transmitted than in the case of the abovementioned state of the part, particularly at higher temperatures, without the main body and/or the molding suffering permanent deformation or the ball head being pulled out of the main body which would be unacceptable. This guarantees absence of backlash or very little backlash at the articulated connection and greater safety against pulling out.
The main body and the molding which form parts of the locator section for the ball head are each provided with a spherical cup to produce surface contact between the ball head and the locator section which would be almost non-wearing.
In principle, it is possible to provide the part of the locator section positively locating the ball head on the main body side with a small undercut in the direction of the joint duct so that the ball head can be snapped into the main body when assembling the articulated connection, before inserting the molding into the joint duct. However, a design is preferred according to which the inside dimension of the joint duct in the main body is greater or the same as the diameter of the ball head at each point of the joint duct. This allows on the other hand joining the ball head to the main body to advantage mainly without applying a force. On the other hand, making the injection cast main body preferably from plastic is simplified according to claim 12 because it is not necessary to release the main body from the mold by force and thus no specific mold release sequence needs to be observed. In addition, a design of the locator section for the ball head on the main body side without an undercut in the direction of the joint duct allows the base body to be released economically from the mold immediately after the injection casting process. If there were an undercut at the main body in the direction of the joint duct, the injection cast main body would first have to cool down for a certain time before it could be released from the mold; otherwise, there would be a risk of permanently deforming the undercut while releasing a warm main body from the mold, possibly resulting in unacceptable backlash in the articulated connection during operation.
The molding at the main body can be fixed by means of a snap connection. This feature facilitates assembly of the articulated connection because the molding inserted into the joint duct of the main body cannot drop out of the joint duct of the main body when joining the main body to the control element. The joint duct can have a suitable recess for positive location of the molding, this recess having a section protruding to the inside at the open end of the joint duct which, as part of the snap connection, engages the molding towards the back in its inserted position in the joint duct.
The main body may be provided with locating lugs clicking into the recesses in the control element to hold the main body positively at the control element. The main body of this design makes the articulated connection simple and economical to assemble.
The main body, viewed from above, may be generally U-shaped, having a base in which part of the locating section is shaped to provide a positive hold for the ball head and two arms extending away from the base which have the locating lugs on them and delimit the opening area for the control rod. The main body can be easily set to a defined position at the control element if the main body base is provided with a traverse slot on the side away from the locating section for positively locating the ball head.
The main body and/or the molding may be provided with protrusions, the purpose of which is to compensate any tolerances to advantage. Assembling the articulated connection is made easier if each of the protrusions at the main body and/or the molding has a bevel which is on the side facing the control element when joining it to the control element.